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Search Results: 1 - 10 of 55 matches for " Thorium "
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ThO2 and (U,Th)O2 processing—A review  [PDF]
Palanki Balakrishna
Natural Science (NS) , 2012, DOI: 10.4236/ns.2012.431123
Abstract: India is one of the few countries committed to expansion of nuclear power. In view of the abundance of thorium relative to uranium, thorium cycle is under serious development and implementation. Both ThO2 and (U,Th)O2 are used. Fine powders of the same are mostly prepared through the aqueous chemical route, pressed and sintered. Extrusion and hot impact densification are also being used. Sol-gel method and other alternatives are also being pursued with the advantage of automation and remote operation. Relevant papers on the thorium cycle with emphasis on processing methods and related aspects are reviewed here.
Fabrication of Thorium and Thorium Dioxide  [PDF]
Balakrishna Palanki
Natural Science (NS) , 2015, DOI: 10.4236/ns.2015.71002
Abstract: Thorium based nuclear fuel is of immense interest to India by virtue of the abundance of Thorium and relative shortage of Uranium. Thorium metal tubes were being cold drawn using copper as cladding to prevent die seizure. After cold drawing, the copper was removed by dissolution in nitric acid. Thorium does not dissolve being passivated by nitric acid. Initially the copper cladding was carried out by inserting copper tubes inside and outside the thorium metal tube. In an innovative development, the mechanical cladding with copper was replaced by electroplated copper with a remarkable improvement in thorium tube acceptance rates. Oxalate derived thoria powder was found to require lower compaction pressures compared to ammonium diuranate derived urania powders to attain the same green compact density. However, the green pellets of thoria were fragile and chipped during handling. The strength improved after introducing a ball milling step before compaction and maintaining the green density above the specified value. Alternatively, binders were used later for greater handling strength. Magnesia was conventionally being used as dopant to enhance the sinterability of thoria. The normal sintering temperature for magnesia doped thoria was 1600 - 1700, which was achieved in electrically heated molybdenum element sintering furnaces with reducing atmosphere. 0.25 mole percent addition of niobia to the thoria was found to bring down the sintering temperature to 1150. Sintering could be done in ordinary furnaces in air atmosphere using silicon carbide or Kanthal heating elements. Electrical conductivity was measured for both magnesia and niobia doped sintered thoria and used in interpreting differences in sintering behavior.
Influence of Co-Solvent on the Extraction Behaviour of Uranium and Thorium Nitrates with Organophosphorous Compounds  [PDF]
K. C. Pitchaiah, K. Sujatha, C. V. S. Brahmmananda Rao, N. Sivaraman, T. G. Srinivasan, K. Nagarajan, P. R. Vasudeva Rao
International Journal of Analytical Mass Spectrometry and Chromatography (IJAMSC) , 2014, DOI: 10.4236/ijamsc.2014.22004
Abstract:

Supercritical Fluid Extraction (SFE) is emerging as a powerful technique in the extraction of metal ions. In the present study, the extraction of nitrates of uranium and thorium was carried out using supercritical carbon dioxide (Sc-CO2) modified with various organophosphorous compounds such as dialkylalkyl phosphonates, trialkyl phosphates and trialkyl phosphine oxides in the presence of co-solvents such as methanol, dichlormethane and n-hexane. The influence of ligand and co-solvent on the extraction of the metal nitrates was studied in detail. These studies have established that co-solvent plays an important role in the extraction as well as fractionation of uranium and thorium nitrates. Polar co-solvent, methanol provided faster extraction without fractionation whereas the non-polar solvent, e.g. n-hexane provided some fractionation of metal nitrates though the extraction kinetics was slower.

Application of a Mathematical Model to the Sierra Indiana Ore Leaching Process Containing Thorium, by Means of H2SO4 Solution and HCl  [PDF]
Pedro Orrego, Peter Fleming, Jorge Skeet, Ramón ávila
World Journal of Nuclear Science and Technology (WJNST) , 2019, DOI: 10.4236/wjnst.2019.91002
Abstract:

The existence of the thorium element in the ores from the Atacama region, Chile, and its importance in the activities of the nuclear industry, have generated the interest of the Chilean Nuclear Energy Commission (CChEN) to study the technical feasibility of its recovery, like ThO2 through the implementation of hydrometallurgical techniques, such as leaching, solvent extraction, among others. The present work has become a report about the research carried out in the Extractive Metallurgy Area of the Department of Advanced Materials of CChEN, whose objective is to know the behavior of the thorium element when the mineral carrier is leached. The leaching tests were carried out in a glass reactor in batch mode, by mechanical agitation, varying different operational parameters, such as: type of leaching solution, concentration of acid in the solution, system temperature and granulometry of the mineral. The results indicate that there is technical feasibility for the recovery of thorium by leaching the mineral carrier with hydrochloric and/or sulfuric solution. The highest recovery of thorium for a sulfuric solution was 70.0% and for a hydrochloric solution of 83.8%, so the process presents a good efficiency in both cases. For a hydrochloric solution, the mathematical model of the thorium recovery efficiency obtained is:

Y=31.14+26.25*X1+8.69*X20.82*X3+9.5*X120.83*X133.71*X231.83*X123+6.45

The concentration of HCl and temperature, as well as their interaction, significantly affect the recovery of thorium for Sierra Indiana mineral, as well as temperature and granulometry. The previous model gives a good representativeness of 99.98%. For a sulfuric solution, the mathematical model of the thorium recovery efficiency obtained is:

Y=29.78+25.92*X1+0.99*X2−1.05*X3−2.05*X129.84*X13−5.26*X23−3.87*X123+15.18

The model indicates

Potentiometric and conductometric studies on the formation of thorium molybdates as a function of pH
Prasad, Shiva;Gon?alves, Sílvia B.;
Journal of the Brazilian Chemical Society , 2000, DOI: 10.1590/S0103-50532000000200018
Abstract: the formation of thorium molybdates obtained by interaction of thorium nitrate and sodium molybdate at specific ph levels 7.8, 5.5 and 4.1 have been studied by electrometric techniques involving ph and conductometric titrations. the well-defined inflections and breaks in titration curves provide cogent evidence for the formation of thorium normal-tho2.2moo3 and para-3tho2.14moo3 molybdates in the vicinity of ph 5.3 and 4.4, respectively. analytical investigations on the precipitates of thorium molybdates have also been carried out, which support the electrometric results.
Potentiometric and conductometric studies on the formation of thorium molybdates as a function of pH
Prasad Shiva,Gon?alves Sílvia B.
Journal of the Brazilian Chemical Society , 2000,
Abstract: The formation of thorium molybdates obtained by interaction of thorium nitrate and sodium molybdate at specific pH levels 7.8, 5.5 and 4.1 have been studied by electrometric techniques involving pH and conductometric titrations. The well-defined inflections and breaks in titration curves provide cogent evidence for the formation of thorium normal-ThO2.2MoO3 and para-3ThO2.14MoO3 molybdates in the vicinity of pH 5.3 and 4.4, respectively. Analytical investigations on the precipitates of thorium molybdates have also been carried out, which support the electrometric results.
Petrographic, Radiometric and Paleomagnetic Studies for Some Alkaline Rocks, South Nusab El Balgum Mass Complex, South Western Desert, Egypt  [PDF]
Ragaa A. M. Elsayed, Hassan M. Assran, Soliman A. Abu Elatta
Geomaterials (GM) , 2014, DOI: 10.4236/gm.2014.41004
Abstract:

Nusab El Balgum mass complex represents one of the alkaline igneous activities in the south Western Desert of Egypt. Petrographic investigations defined some different rock types in south of the complex represented by alkaline volcanics (pyroclastics [rhyolitic crystal tuffs], spherulitic rhyolites, alkaline rhyolite dykes), sub-volcanic peralkaline granites and structurally controlled mylonitic volcanoclastics. These rocks recorded significant concentrations in terms of the two radioactive elements Th and eU, which displayed considerable spatial variations, especially within the peralkaline granites. The abundance of Th and eU is mainly related to favorable combination of structural and pos-magmatic hydrothermal conditions. Paleomagnetic results give well-defined stable remanent magnetization directions of reliable VGP positions, which are presented and discussed in the context of the African APWP. Rock types, magnetization directions and VGP positions with the corresponding ages are as follows: 1) Rhyolitic crystal tuffs; D/I = 340.0°/—19.4°, α95 = 6.8°; VGP Lat./Long. = 51.4°N/240.5°E, A95 = 5.9° (Late Triassic). 2) Spherulitic rhyolites; D/I = 346.7

Gamma-Ray Spectrometry and Induced Polarization Studies for El Atshan-II Uranium Prospect Area, Central Eastern Desert, Egypt  [PDF]
Assran S. M. Assran, Ragaa A. M. Elsayed, Hosni H. Ghazala, Hussein F. Abdelsalam
Geomaterials (GM) , 2014, DOI: 10.4236/gm.2014.43010
Abstract:
Gamma-ray spectrometry and induced polarization (IP) studies were carried out to determine the radioactive anomalous zones and to follow their lateral and vertical extensions in El Atshan-II uranium prospect area, central Eastern Desert, Egypt. This area and its surroundings are covered by different Precambrian basement rocks, which intruded by younger bostonite rock, andesite dykes and carbonate veins. Data of the gamma-ray spectrometry have been analyzed qualitatively and quantitatively by applying specific interpretation techniques. These data revealed a wide radioactivity range oscillating from 15.0 to 2362.0 Ur, 0.5 to 307.2 ppm, 0.1 to 55.1 ppm and 0.3 to 22.0% for the total count (Tc), equivalent uranium (eU), equivalent thorium (eTh) and potassium (K), respectively. The constructed radioelement concentration maps and eU-composite image of the study area showed that the anomalously high radioactivity levels are mainly associated with outcrops of the bostonite rock. The induced polarization data were mathematically inverted to produce the true resistivity and chargeability values of cross-sections below the surveyed lines traverse in the area. The resistivity values are varied both vertically and horizontally from 7.83 to more than 1042.0 ohm·m, while the chargeability values are ranged from 0.195 to more than 204.0 mV/V, suggesting variation of the rocks facies and mineralizations. Integration of the resistivity and chargeability data indicates the presence of some mineralized zones, mainly associated with the bostonite rock, with depths varied from the near-surface to more than 70 m. Therefore, a core drilling is recommended at some stations along three selected profiles to a depth of 70 - 100 m to test the depth, structural model and grade of mineralization in the area.
Simulation of an Accelerator Driven Subcritical Core with Mixed Uranium-Thorium Fuel  [PDF]
Ali Pazirandeh, Laia Shirmohammadi
World Journal of Engineering and Technology (WJET) , 2015, DOI: 10.4236/wjet.2015.33C049
Abstract:

During recent years, a new generation of nuclear reactors, known as “Accelerator Driven Subcritical Reactors”, has been developed. One of the new application aspects for such reactors (besides transmutation of High Level Waste and burning Minor Actinides) is usage of thorium as nuclear fuel. In this work a subcritical core in experimental scale is simulated by MCNPX code. The core contains two types of fuel assemblies: (85% ThO2 + 15% UO2) and MOX (U-Pu). In the first step, only the thorium-contained fuel assemblies are loaded into the core. Criticality calculations using MCNPX show that the keff is so low that the fuel assemblies cannot run the subcritical core. This implies that MOX (U-Pu) assemblies must be loaded as well. Neutronic parameters of the thorium- fueled Accelerator Driven Subcritical core are then calculated as well as some other parameters related to accelerator coupled with the core. The main objective of this simulation is to study the behavior of Accelerator Driven Subcritical core with thorium assemblies.

Characterization of Crude Oil, Asphaltenes Based on Bismuth (Bi), Thorium (Th) and Uranium (U) Levels: Potential Environmental Impact  [PDF]
Amr Abd Elhameed, Avin Pillay, Roger Nunn, Sasi Stephen
Journal of Environmental Protection (JEP) , 2016, DOI: 10.4236/jep.2016.72017
Abstract: The actinides (Th, U) and bismuth exist at ultra-trace levels in petroleum and have rarely been reported to characterize combustible fuels. However, high-performance mass spectrometry coupled with plasma technology has succeeded in reaching detectable limits in the ng/L range, and has thus made such characterization possible. Crude oil is used as sludge for certain agricultural purposes; and asphaltenes are converted to by-products for constructing car parks, pavements, roofing material and thoroughfares. Our study uncovers an area that has not been previously explored and we examine the potential ecotoxicology of bismuth, thorium and uranium in this context. Asphaltene derivatives were separated from crude oil samples via multiple-stage soxhlet extraction. The virgin crude oil and isolated asphaltenes were investigated for Bi, Th and U content using a high-powered hyphenated facility. A Perkin Elmer SCIEX DRC-e ICP coupled to a quadrupole mass spectrometer was employed to detect the elements of interest. The levels of these elements occurred in the mg/L (ppm) and μg/L (ppb) ranges and were compared for crude oil and asphaltenes. The data showed higher levels of the detected elements in the asphaltene phase. The feasibility of applying the experimental results as a fingerprinting tool for provenancing crude oil and asphaltenes was examined. The results are discussed from the perspective of bismuth and actinide pollution and its long-term impact on sustainable development.
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